[RC-Monster Mike]

MadDog and Patch: welcome to the forums to both of you! Thanks for jumping right in as well, Patch! Between what HotnCold and Patch have mentioned, the ground is pretty well covered, but I will add a few possibilities based on the information presented.

The weird noise at low or partial throttle from takeoff is perfectly normal. All the Warrior controllers do it (sounds like a whine almost) as they takeoff. No worries there. The back of the motor shouldn't come off, but it is only pressed on, so it certainly can happen. I should have a fix for this any time now. I am working on a prototype heat sink for the motor that also acts like a motor clamp, and should have these available soon.

The jerk you are describing from a dead stop (back and forth motion) is a result of low BEC voltage. This means your batteries are dropping below 5.5 volts (if you are running 12 cells, you have crappy batteries). This typically does not happen with a receiver pack in place, either. I think a good set of batteries and the motor clamp/heatsink I am working on will cure your problems altogether. Start with a nice set of batteries (try someone elses if you have the opportunity to see the difference). Stick with good batteries (stay away from orion packs or similar cheap packs, as they can't deliver the voltage/amps required to fully enjoy your system).